1. Field of the invention
The invention lies in the field of recovering the metals manganese, nickel and cobalt from the oxide and silicate ores by hydrometallurgical procedures.
2. Description of the Prior Art
A great many processes have been developed for the recovery of nickel and cobalt from the extensive, known laterite deposits. While practiced commercially, these processes are all expensive. This expense reflects the high cost of processing and recovering nickel and cobalt where their content in the feed material may be only 1-2 percent nickel and 0.05-0.2 percent cobalt. One of the major problems to be overcome is that the deposits contain large amounts of iron oxides such as goethite. The iron is difficult to isolate chemically and still achieve a high recovery of the small amounts of contained nickel and cobalt. Similarly, sea nodules have been found in quantity in ocean beds. These nodules again contain small amounts of nickel and cobalt with substantial amounts of manganese and iron oxide. The high cost of extracting the nickel and cobalt from such a source, where the content is less than two percent, has been one of the factors which has prevented the exploitation of recovery of those metals from sea nodules.
Among the processes which have been proposed for recovering metal values from lateritic nickel has been the selective reduction of nickel and cobalt to metallic state without co-reducing iron. It has been known to add certain chlorides such as sodium chloride and calcium chloride to promote the reduction. Subsequently the nickel and cobalt can be redissolved with lixiviants which are specific to these metals, as opposed to iron oxide.
A number of processes have been proposed for recovering metal values from sea nodules including the total dissolution of the metal values including iron oxide in strong hydrochloric acid. The reaction of manganese dioxide and hydrochloric acid yields the pollutant chlorine as a product. Further, the process is very expensive and difficult.